Food receptacle comprising a reheating device by exothermal reaction of two reactive products

ABSTRACT

The receptacle (1) is comprised of two parts (A) and (B) containing, on the one hand the heater (5) and on the other hand a canned food product (30). A ladle (9) containing water rests on the bottom of the heater (5). A strip (20) enables to tear the ladle (9) without touching the cover (11) which keeps its function of isolating the two volumes (A) and (B) while cooperating with the bottom (32) of the food canned (30) to transmit by conduction and radiation the calories emitted during the exothermal reaction. A flange of the receptacle (11) enables to seal all along its contour the can (30) and an out== isolating package (3) enables to handle the receptacle (1) without any risk during the operation of the heater (5). The sealing of the assembly is completed by a wax or compound seal at the outlet of the strip (20). The invention applies both to the domestic and collective catering.

The invention relates to a food tray including a heating device usingthe exothermic reaction of two reactive products.

Heating foods, culinary preparations, drinks in particular is knownusing the exothermic reaction for example of quick lime and water.Although the principle is simple, because it is based on a chemicalreaction whose equation is known, on the other hand the practicalapplication thereof is much less so. Numerous devices have beenprovided, but all come up against a few major problems: safety inoperation on the one hand and efficiency on the other.

In so far as safety in operation is concerned, the reaction must takeplace more especially without the risk of burning for the user and theproduct to be consumed must be isolated sealingly from the reactiveproducts and finally there must be good preservation of this productthrough insulation, also as tight as possible, from the external medium.

As for the efficiency, all depends on the reaction itself which must becomplete, with optimized heat exchanges between the heater and thefoods.

The aim of the present invention is to overcome all these problems. Itrelates more precisely to a food tray equipped with a reliable andefficient independent heater, in which the product to be heated isperfectly protected against any aggression from the reactive products,but on the other hand is in perfect thermal contact with the heat fromthe exothermic reaction, without it being necessary to use for thisheating the steam released during the reaction which, moreover, onlyoccurs for a very short time and proves insufficient.

It also relates to such a tray adapted for sealed closure of the wholewhich ensures good preservation thereof.

It relates finally to a tray cooperating with an insulating packing(external skirt) which allows the user, without the risk of burning, tohandle the tray during and after heating.

The invention relates more precisely to a food tray including a heatingdevice using the exothermic reaction of two reactive products,characterized in that the two parts or volumes (A) and (B) of the tray(1) receiving respectively the heater and the food receptacle areseparated by a cover which provides insulation between the two parts (A)and (B) before and during the reaction while cooperating with the bottomof the food receptacle so as to ensure, by contact, the conduction andradiation of the heat from the heater towards the products to be heatedcontained in said receptacle, this latter having a profile complementaryto the inner profile of part (B) of the container and its peripherywhile itself being closed by a lid isolating the contents of the foodreceptacle from the outside.

The invention will be better understood from the following explanationsand the accompanying Figures in which:

FIG. 1 illustrates schematically the architecture of the different meansused in a tray according to the invention,

FIGS. 2 and 3 illustrate the position of the tongue for opening thewater pocket, and

FIGS. 4 to 7 show different variants for the sealed external closure ofsaid container.

For the sake of clarity, the same elements bear the same references inall the Figures.

As shown in FIG. 1, a tray 1 includes two parts: the first A containingthe heater properly speaking and the second B containing the foodreceptacle or preserve. According to an important feature of theinvention, this tray 1, made for example from polypropylene, includes ashoulder 2 which serves as support point when this tray is inserted inan external packing 3 made for example from polystyrene whose functionis to isolate the user thermally from said tray 1 when the heater isoperating. To further improve the heat insulation and according to yetanother feature of the invention, the inside of tray 1 is lined with anequally insulating material, such as cardboard. This lining 4 is in theform of a box and rests on the bottom of part A. The heater properlyspeaking is formed by a coated or complexed aluminium container 5. Thiscontainer has a shoulder 6 on which bear two wings 7 and 8 integral witha sealed pocket 9 which rests on the bottom 10 of said container 5. Acover 11 hermetically closes this part A corresponding to heater 5.Pocket 9 contains one of the mutually isolated reactive products, inthis case water, whereas in a part of the free volume of the heater 5situated above pocket 9 is disposed the second reagent, for examplequick lime 15.

According to another important feature of the invention, and as shownmore particularly in FIGS. 2 and 3 showing the pocket 9, seenrespectively from the top and from the bottom, the pocket 9 is equippedwith means for comingling the reactive products in the form of anopening ribbon 20 which surrounds it. An end a of this ribbon is bondedor welded to the upper part of the pocket at the level of a zone S. Theribbon is folded back on one side of the pocket 9 in which a breakagezone 21 has been formed. This ribbon 20 passes freely round the lowerface of pocket 9 so as to extend outwardly beyond the other wing. Theother end b of ribbon 20 extends then (FIG. 1) outwardly of heater 5while passing through, without damaging it, a first seal formed betweenthe cover 11 and heater 5, this seal being for example made from wax andallowing free sliding of ribbon 20.

The part B of the tray 1 receives the food preserve (FIG. 1) orreceptacle (both bearing the reference 30) containing the product 31 tobe heated, closed for the preserve by a presealed lid 35 and for thereceptacle by a lid 350, as will be illustrated in the followingFigures, both forming an insulation for the product to be consumed 31with respect to the external environment.

In accordance with the invention, the bottom 32 of the receptacle orthis preserve 30 is in intimate contact with the closure lid of theheater 5.

For greater clarity in FIG. 1, the bottom 32 and cover 11 are movedslightly away from each other which, in fact, are superimposed. Underthese conditions, heating of the product to be consumed is obtained bothby conduction and by radiation.

This receptacle or presergve 30, according to an important feature ofthe invention, has a profile complementary to that of the tray 1 and hasat the level of the seal a flat edge 300 providing a tight seal,technically easy to carry out on the periphery 1a of tray 1. Theseprofiles are illustrated in FIGS. 5 to 7 showing, by way of nonlimitative examples, four variants of sealing the receptacle or preserve30 containing the food product 31, to the tray 1 through said flat edges300 on the periphery 1a of this tray 1.

A first variant (FIG. 4) consists in providing a flat edge 300 at thelevel of receptacle 30, so that it can be bent back at R about theperiphery 1a of tray 1 before heat sealing an external lid 350 on theperiphery 1a. This heat sealing is carried out on complexed materials.

A second variant (FIG. 5) consists in an over-molding 90 by injectionwhich seals the edges 300 of lid 34 of preserve 30 to the periphery 1aof tray 1.

In a third variant (FIG. 6), the edges of the lid 350 project beyond theperiphery, which allows simultaneous sealing of the food receptacle 30and of the edges of the lid to the tray 1.

Finally, a fourth variant consists in using mechanical crimping 91.

In all cases, so as to complete sealing with the outer environment, asecond seal formed for example from wax, mastic or an equivalentmaterial, is formed at the exit of ribbon 20 and of the lid 35, 350.

From the above description the main characteristics of the presentinvention can be clearly seen.

On the other hand, the thermal contact between the bottom of the foodreceptacle 30 and the cover 11 allows heat conduction. On the otherhand, the materials used for manufacturing the heater 5 and cover 11 arechosen from the range of good conducting materials.

Experience in fact shows that, during the heating cycle up to theheating peak which takes place approximately after 12 to 15 minutes, theemission of steam at 90° to 100° only appears during the first minute ofthe exothermic reaction. This steam, if it acts alone, is incapable ofraising the temperature of the food receptacle under good conditions. Onthe other hand, in the device of the invention, the expansion of thelime during the reaction, which doubles in volume with respect to theinitial volume, is used for further contributing to placing cover 11 incontact with bottom 32. With the temperature of the reactive mixturereaching values close to 300° to 330°, the mass of lime then heats thefood receptacle 30 and its contents 31 without difficulty, allconditions being equal (amount of product to be heated, amount ofcompression of this product . . . ).

Under these conditions knowing the equation of the reaction, the amountof water used may be optimized, all the more so since the member foropening the pocket 9, namely the ribbon 20, through its design andimplementation, allows the water to diffuse evenly over the largestpossible area of lime. By way of example, the grain size of the limecorresponds to grains greater than a section of 2 millimeters square.

Heating is obtained without it being necessary to destroy the cover 11even partially, which, on the contrary, maintains its role as separator(in every other respect than that of heat conduction) between thereactive medium and the element to be heated.

Thus, the water vapor is confined as much as possible and contributes,not to heating the food, but on the contrary to promoting correctevolution of the exothermic reaction. This protection by cover 11mitigates the possible consequences of lime overflow in the case of amishap in handling.

Finally, the positioning of the cardboard liner 4 and the outerpolystyrene packing 3 keeps a maximum of heat inside the tray, whichbenefits heating, and the user can handle the tray without danger forthe heat on the outside of this packing remains lower than 60°.

Such a self heating tray, in accordance with the invention, findsapplications not only for use by individuals but also in group catering.

We claim:
 1. A food tray including a heating device using an exothermicreaction between two reactive products, comprising:a tray element havingan open top; a heater fitted in said tray element and comprising aheater container, mutually isolated exothermic reactive products fittedin said container and a heat conductive cover hermetically sealing saidcontainer; a food receptacle fitted in said tray element and having asurface in contact with said cover, whereby conductive heat transferthrough said cover and to said food receptacle may be accomplished; alid sealingly closing said open top; and means external to said foodtray and extending into said heater container for comingling saidreactive products to produce an exothermic reaction without damaging ahermetic sealing integrity of said cover, whereby said comingledreactive products are hermetically sealed in said tray element.
 2. Thetray according to claim 1, wherein said tray element has a peripheralflange, including means for sealing said lid to said flange.
 3. The trayaccording to claim 2, wherein said sealing means comprises the edge ofsaid lid being folded back onto said flange.
 4. The tray according toclaim 2, wherein said sealing means comprises a heat sealing of saidlid, said food receptacle and said flange.
 5. The tray according toclaim 2, wherein said sealing means comprises an over-molding fittedaround said lid and said flange.
 6. The tray according to claim 2,wherein said sealing means comprises a metal ring crimped about saidflange and said lid.
 7. The tray according to claim 1, wherein saidheater container has an annular shoulder, including a pocket withinwhich is sealed one of said mutually isolated exothermic reactiveproducts, said pocket having two wings supported by said shoulder, saidpocket resting on a bottom of said heater container, and wherein theother of said mutually isolated exothermic reactive products is externalto said pocket.
 8. The tray according to claim 7, wherein said pocketdefines a breakage beginning zone, and wherein said means for cominglingcomprise a ribbon having one end fixed to said pocket at said breakagebeginning zone, said ribbon passing around the bottom of said pocket. 9.The tray according to claim 1, including insulating means on said heatercontainer.
 10. The tray according to claim 8, wherein said ribbon passesout of said heater container at a joint between said heater containerand said cover, said joint including a seal.